Examples of electronically controlled cartridge control valves for fuel injectors are shown in U.S. Pat. No. 5,494,219 to Maley et al., U.S. Pat. No. 5,407,131 to Maley et al., U.S. Pat. No. 4,869,462 to Logie et al., and U.S. Pat. No. 4,717,118 to Potter. In each of these examples, the injector includes a mechanically actuated fuel pumping plunger and an electronically actuated fuel pressure control valve assembly. The pressure control valve assembly includes a solenoid operated poppet valve that controls fuel pressure in the injector in order to control fuel injection delivery. Fuel pressure is controllably enabled to be developed within the injector by electrical actuation of the pressure control valve assembly. Fuel pressure is controllably prevented from developing within the injector by not electrically actuating the pressure control valve so that fuel can spill through a return passage while the plunger is undergoing a portion of its pumping stroke.
In such electronically controlled fuel injectors, the armature of the pressure control valve assembly moves the poppet valve in one direction until it engages a valve seat, and holds the poppet valve in its closed position to enable fuel pressure to be developed in the injector, eventually resulting in fuel injection. At the end of the fuel injection cycle, the solenoid is de-energized, and a return spring moves the poppet valve member off the valve seat, returning the poppet valve member to its open position, which prevents the development of fuel pressure by spilling the fuel back to a fuel reservoir.
With reference to Maley et al. patents identified earlier, they achieved a break through in cartridge control valves through the use of a valve member with an annular knife edge that seats against a flat valve seat. The advantage of this knife edge/flat seat sealing is that less force is required to hold the valve closed at a given pressure and also opens with less force than the conically seated poppet valve members of the prior art. In addition, the flat seat design requires less valve member stroke movement than conventional conical valve seats to achieve a given flow area across the seat for a given valve member diameter. Although the Maley et al. control valves have achieved these advantages, there remains room for improvement. For example, the solenoid coil in Maley et al. '131 must be embedded within the valve body, which limits the size of the coil and the corresponding force it can produce. An innovation that permits the use of a larger coil in conjunction with the Maley et al. flat seating could further improve the control valves' performance. In addition, there remains room for improvement in decreasing the over all number of parts in the control valve assembly, as well as the ease with which those parts can be assembled in a production environment. Finally, any innovation that would decrease the number of valve components exposed to high pressure would also be an improvement since decreasing the number of components exposed to high pressure improves the robustness and the working life of the control valve.
The present invention is directed to improving upon cartridge control valves of the prior art.